Screen system

Abstract

The present invention provides a screen system (8) suitable for use in a vibratory screen apparatus (1), and comprising: a screen element (11) and a support frame (12) therefor, as well novel screen elements (11) and mesh panels (19) therefor, and the use thereof. The screen element (11) consists essentially of a mesh panel (19) provided with first and second elongate support members (22, 23) extending along opposite end portions of the mesh panel (19). The support frame (12) has spaced apart first second elongate frame elements (13, 14) for engagement with the screen element support members (22, 23) and further elongate frame elements (17, 18) extending there between for supporting the mesh panel (19). The screen element support members (22, 23) and said first and second frame elements (13, 14) are formed and arranged for secure interengagement in use of the screen system, with at least one of said screen element support members and the respective one of said first and second frame elements being formed and arranged so that when clamped together, the mesh panel (19) is securely held under tension against said further frame elements (17, 18).

Description

FIELD OF THE INVENTION[0001]The present invention relates to screen systems for use in vibratory screen apparatus suitable for use in liquid solid separation and classification including inter alia, the sifting of drilling mud, cuttings and like material derived from oil-well drilling.BACKGROUND OF THE INVENTION[0002]Conventional vibratory apparatus for sifting mud and like material in the oil industry generally utilise screens of either hook strip or pretensioned design. Hook strip screens generally consist of single or multiple layers of mesh bonded together, which are tensioned after mounting in the basket of the vibratory screen apparatus. Two opposed ends of the screen are fitted with a turn back element to form a hook strip which is hooked around a tension rail, the latter being attached to the side wall of the basket, typically via a tension bolt, though other loading means to apply tensioning and securing forces may be employed. Tightening the tension bolt moves the tension ...

AI Technical Summary

Benefits of technology

[0009]It is an object of the present invention to avoid or minimize one or more of the above disadvantages.

Problems solved by technology

Hook strip screens have a number of disadvantages including the complex and time consuming mounting of the screen members in the basket, which results in significant downtime of the vibratory screen apparatus and requires the use of multiple parts.

Attaining the correct screen tension for the material to be sieved also involves intricate fine tuning and the screens are easily damaged if too much force is applied when tightening the bolts or loading means to tension the screens.

A further disadvantage is the relatively poor sealing between the screen and basket.

The metal on metal seal often results in leakage with unscreened material passing through gaps between the screen and the basket, and mixing with already screened material below the mesh screen.

Attempts to overcome the poor seal by placing rubber strips or gaskets at the metal / metal interfaces have proved unsatisfactory.

These require intricate and time consuming fitting and frequently work loose during vibration and become lost or lodged in the vibratory machine, obstructing and damaging the machinery.

In addition applying tension to the screen when tightening the tension bolt or loading means gives rise to additional stresses over and above those already suffered by the machine framework due to the vibratory motion, thereby possibly resulting in deterioration of the framework.

Conventional pretensioned screen units with integral support frames have significant disadvantages being bulky, heavy and difficult to handle, transport and store; all very major considerations for use on off shore installations where all of these are at a very high premium.

The design is complex and the frames expensive to construct.

The frames utilise large amounts of material all of which require disposal when the screen units are replaced, which is both inconvenient and expensive and has a negative impact on the environment.

These screen assemblies, however, are very complex in structure with many of the disadvantages and associated expense of conventional pretensioned screens and, in addition, the inconvenience, storage and additional material requirements of the modules.

A further problem that arises with known screen systems is that due to the extra weight of the material being processed which is concentrated, in use of screening apparatus at the back (upstream) end thereof.

The screen mesh in that area is subjected to particularly heavy wear resulting in the frequent need for replacement thereof.

This problem has previously been addressed by using coarser heavy duty mesh in that area, but this inevitably results in reduced screening performance of the screening apparatus.

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